What Is a Fifth Wheel Trailer Hitch? | Kingpin Towing Explained

If you’ve ever seen a large RV trailer being pulled by a pickup truck, there’s a good chance it was using a fifth wheel hitch. Unlike a conventional ball hitch that attaches to a receiver at the rear bumper, a fifth wheel hitch mounts inside the truck bed, directly over or just ahead of the rear axle. This placement transfers the trailer’s weight more evenly across the truck’s frame, creating a stable towing platform that handles heavy loads with noticeably less sway.

How the Hitch Mechanism Works

A fifth wheel hitch uses two main components: a set of locking jaws or a locking bar mounted in the truck bed, and a kingpin on the front of the trailer. The trailer’s kingpin drops into the hitch’s head, and the jaws clamp securely around it. The head plate or pivoting head then allows the trailer to articulate during turns and over uneven road surfaces, keeping both truck and trailer stable.

The hookup process is straightforward once you’ve done it a few times. Lower the truck’s tailgate, back the truck to within about 4 or 5 inches of the kingpin, and open the jaw handle. After setting the trailer height so the kingpin sits flush with the hitch plate, back in slowly until the pin slots into the jaws. You’ll hear a solid clunk when it engages. Always secure the safety pin or lock before pulling away.

Fifth Wheel vs. Gooseneck: What’s the Difference?

Both systems mount in the truck bed, but they use different connection points. A gooseneck trailer has a ball mounted in the bed floor with a trailer that uses a coupler dropping straight down; fifth wheel hitches use the raised head plate and kingpin design. CURT Manufacturing’s gooseneck adapter explainer notes that gooseneck adapters allow fifth wheel trailers to connect to gooseneck ball installations, providing flexibility if you already have a gooseneck setup. For most heavy RV towing, a dedicated fifth wheel hitch remains the standard because of its wide, flat head plate that distributes forces evenly during sharp turns.

Fixed vs. Sliding: Which Configuration Fits?

Fixed fifth wheel hitches are the most common and straightforward design. They don’t move fore-and-aft in the truck bed, making them simpler to install and maintain. Sliding hitches, on the other hand, allow the hitch head to move backward on rails when the truck bed length creates clearance issues during tight turns. If you’re towing a long fifth wheel trailer with a short-bed pickup, a sliding hitch prevents the trailer cab from contacting the truck cab during maneuvering.

Above-bed installations are the most typical aftermarket setup, with the entire hitch sitting on top of the truck bed floor. Below-bed systems exist for trucks with factory puck systems, where the hitch mounts flush with or below the bed surface when not in use, preserving bed space for cargo. Your choice depends on how often you need the full truck bed versus how frequently you tow.

Capacity and Installation Basics

These hitches can handle substantial loads, typically in the 16,000 to 30,000 pound range, though you must verify the specific hitch model and your truck’s payload rating before committing. CURT’s fifth wheel hitch guide emphasizes that installation always begins with level ground, parking brake engaged, and wheel chocks in place. Dry-fit the hitch in the bed to confirm it sits level and centered before drilling any mounting holes. If your system requires drilling, follow the manufacturer’s exact hole pattern and torque every bolt with a torque wrench to the specified setting.

If you’re shopping for your first setup and want to compare top-rated models side by side, our tested roundup of the best fifth wheel trailer hitches covers what works best for different truck lengths and towing weights.

Compatibility starts with the trailer itself: it must have a kingpin, not a bumper coupler. The installation method also varies by truck — industry standard rails, factory puck systems, and gooseneck mounts are all common. J.D. Power’s fifth wheel trailer hitch guide confirms that selecting the right hitch requires matching the system to both your truck bed layout and your trailer’s connection style.